Localizing value of MEG in refractory partial epilepsy: Surgical outcomes

• Published in: International Congress series 2007-06, Vol.1300, p.657-660
• Main Authors: Manoharan, A., Bowyer, S.M., Mason, K., Tepley, N., Elisevich, K., Smith, B.J., Barkley, G.L.
• Format: Article
• Language: English
• Subjects: Epilepsy surgery; MEG; Outcomes
• ISSN: 0531-5131; 1873-6157
• DOI: 10.1016/j.ics.2007.02.036

A retrospective review was carried out on epilepsy surgery patients with at least 2 years of post surgical outcome data who had MEG scans to localize epileptic foci to determine whether or not MEG had a significant impact on localization and improving likelihood of a seizure free outcome. Brain activity was recorded with 148-channel MEG system and a 32-channel EEG system. Ninety patients (Male = 41, Female = 49; age range 8–66 years) had MEG and MRI scans prior to full presurgical evaluation. Prolonged intracranial (ECoG) recordings were also performed on all patients. Interictal activity was localized in the MEG data in patients using the single equivalent current dipole (ECD) technique. Only patients with Engel Class I or II outcome ( N = 75) were included, with the rare exception of patients who had well localized intracranial ictal patterns, but resection was limited due to overlap with eloquent cortex or multiple independent foci. MEG data, compared to surgical resection or well localized intracranial ictal patterns, were concordant in 22 patients (29%). MEG data provided supplemental information in 10 patients (13%) and novel data in 11 patients (15%). Of the 75 patients in this analysis, 43 (57%) had MEG data that provided additional information for the surgeon. Four of the patients (5%) had data contaminated with artifact. In 25 patients, no spike or sharp activity was seen in MEG data. No age and gender effects were detected. The results show that MEG is useful in localizing the epileptogenic zone as a non-invasive technique before surgical resection. These results provide further evidence that epileptiform activity can be detected non-invasively with MEG, and provide localization information to the surgeon. Thus in 18 of the 75 patients (24%) with Engle Class I or II outcome, MEG provided unique information critical to successful outcome.